Which of the following will reduce the width of a confidence interval for the me

Question

Which of the following will reduce the width of a confidence interval for the mean of a population? i. Increasing the confidence level. ii. Increasing the sample size. iii. Decreasing the standard deviation. A. Only i. B. Only i. and ii. (and not iii.) C. Only ii and iii. (and not i.) D. i., ii., and iii. The mean cholesterol level for a sample of cases of women with hypertension during pregnancy was found to be 212 mg/dL. The lower 95% confidence limit on the population mean was determined as 192 mg/dL. The standard error (of the mean) was (approximately)?

Explanation / Answer

Answer:

12).

C. only ii and iii

13).

Margin of error = 212-192=20

Z value for 95% =1.96

Margin of error = z*standard error

Standard error = margin of error /z =20/1.96

=10.204

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